By forcing extra air into the engine, as realized during the late 19th century by Gottlieb Daimler, a turbocharger may increase engine torque and power output density. The turbocharger may include a turbine driven by expanding exhaust gas that is coupled to a compressor via a drive shaft. The compressor may be fluidly coupled to an air intake manifold in the engine connected to a plurality of engine cylinders. The flow of exhaust originating at one or more of the engine cylinders may be directed to a turbine wheel, driving the rotation of the turbine about a fixed axis. The rotation of the turbine drives the rotation of an impeller (e.g., wheel) of the compressor which compresses air into the air intake manifold to increase boost pressure based on engine operating conditions.
Compressor efficiency influences overall engine performance and fuel consumption. For example, lower compressor efficiency may result in slow engine transient response and higher fuel consumption for both steady-state and transient engine operation. At lighter engine loads, when compressor efficiency is reduced, increased turbocharger lag may result during a tip-in. Additionally, light load operation may result in lower compressor efficiency and compressor surge limits may restrict boost pressure rise at low engine speeds.
Other attempts to address low compressor efficiency include a compressor configured with adjustable inlet guide vanes. One example approach is shown by Hodder in U.S. Patent Application Publication No. 2010/0172745 A1. Therein, a rack and pinion drive mechanism for the adjustment of inlet guide vanes of a compressor is disclosed. The mechanism is positioned within the compressor casing and surrounds a shaft connected to an impeller of the compressor. A ring with a plurality of slots is adapted to couple with a plurality of lever arm assemblies, each having a pin, so that the pins are positioned within each of the slots. A plurality of vanes are coupled to an end of each lever arm with a pinion coupled to the shaft of one of the vanes, acting as a drive vane. The drive vane is configured to rotate a ring via the rack and pinion drive mechanism, thereby pivoting the inlet guide vanes and adjusting the flow of gas through the vanes.
However, the inventors herein have recognized potential issues with such systems. As one example, even in the open position, due to the orientation and pivoting direction of these vanes, flow through the variable inlet device and to the impeller is restricted (e.g., partially blocked). As a result, this type of variable inlet has reduced high end efficiency and constrains high end intake air flow.
In one example, the issues described above may be addressed by a compressor comprising an impeller rotatable about a central axis and an inlet conduit including a variable inlet device (VID) positioned therein, upstream of the impeller. The VID may include a set of semi-cylindrical shells connected to a base that forms a ring around the central axis with inner surfaces of the shells forming a flow passage through the VID, each of the shells being pivotable about a hinge arranged at a mid-point of an inlet edge of each shell, between an open and closed position. In the open position, the inner surfaces of the shells form a uniform flow passage with reduced flow restriction. In the closed position, the shells may be angled so that a diameter of the outlet end is smaller than a diameter of the inlet end of the VID, thereby restricting flow as the flow passes through the flow passage of the VID. As a result, compressor efficiency is increased in the closed position due to the restricted flow that is generated by the VID. Compressor efficiency is further increased at higher loads when the VID is in the open position due to reduced flow restriction through the inlet conduit and VID. In this way, compressor efficiency and overall engine performance and fuel economy may be increased across a wide range of engine operating speeds and loads.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.